Variable pitch fan actuator

ABSTRACT

A gas turbine engine including a core having in serial flow order a compressor, a combustor, and a turbine—the compressor, combustor, and turbine together defining a core air flowpath. The gas turbine engine additionally includes a fan section mechanically coupled to the core, the fan section including a plurality of fan blades, and each of the plurality fan blades defining a pitch axis. An actuation device is operable with the plurality fan blades for rotating the plurality fan blades about their respective pitch axes, the actuation device including an actuator located outward of the core air flowpath to, e.g., simplify the gas turbine engine.

FIELD OF THE INVENTION

The present subject matter relates generally to an actuation device fora variable pitch fan.

BACKGROUND OF THE INVENTION

A gas turbine engine generally includes a fan and a core arranged inflow communication with one another. Additionally, the core of the gasturbine engine generally includes, in serial flow order, a compressorsection, a combustion section, a turbine section, and an exhaustsection. The compressor section, combustion section, and turbine sectiontogether define a core air flowpath therethrough. In particularconfigurations, the turbine section is mechanically coupled to thecompressor section by one or more shafts extending along an axialdirection of the gas turbine engine.

The fan includes a plurality of blades having a radius larger than thecore of the gas turbine engine. The fan and plurality of blades may alsobe mechanically coupled to one of the one or more shafts such that theyrotate along with the turbine. Rotation of the plurality of bladesgenerates thrust for the gas turbine engine and provides airflow to thecompressor section of the core.

For at least some gas turbine engines, the fan is a variable pitch fan.It can be desirable to vary a pitch of the fan blades by rotating theblades about respective pitch axes to further increase performance ofthe gas turbine engine. For example, a primary reason for changing bladepitch is to adjust the blade's angle of attack for optimal performancebased on the present air speed of the aircraft and power level of theengine. Alternatively, the pitch of fan blades may be used to reversethe airflow, bypassing the core of the engine, thus providing reversethrust to aerodynamically brake a landing aircraft.

An actuation member is typically provided in operable communication withthe plurality of fan blades to change the pitch of the plurality of fanblades. More particularly, the actuation member includes an actuatorpackaged within the fan section, typically proximate the plurality offan blades to rotate the plurality of fan blades about respective pitchaxes. However, such a configuration may make it more difficult to repairand/or maintain such actuator. Further, such a configuration mayincrease the complexity of the engine by, e.g., requiring transfers ofpressurized hydraulic fluid from a static frame of reference to arotating frame of reference.

Accordingly, an actuation member having a more accessible actuator wouldbe useful. Additionally, an actuation member having an actuator forrotating the plurality of fan blades that does not require transferringa pressurized hydraulic fluid from a static frame of reference to arotating frame of reference would be particularly beneficial.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

In one exemplary embodiment of the present disclosure, a gas turbineengine is provided. The gas turbine engine includes a core having inserial flow order a compressor, a combustor, and a turbine. Thecompressor, combustor, and turbine together define a core air flowpath.The gas turbine engine also includes a fan section mechanically coupledto the core. The fan section includes a plurality of fan blades, each ofthe plurality of fan blades defining a pitch axis, and the plurality offan blades each rotatable about their respective pitch axis. The gasturbine engine also includes an actuation device operable with theplurality of fan blades for rotating the plurality of fan blades abouttheir respective pitch axes. The actuation device includes an actuatorlocated outward of the core air flowpath.

In another exemplary embodiment of the present disclosure, an actuationdevice for a gas turbine engine is provided. The gas turbine engineincluding a core defining a core air flowpath and a fan sectionmechanically coupled to the core. The fan section includes a pluralityof fan blades each rotatable about a pitch axis. The actuation deviceincludes an actuator configured to be located outward of the core airflowpath of the core when the actuation device is installed in the gasturbine engine. The actuation device additionally includes a connectionassembly extending from the actuator for operably connecting theactuator to the plurality of fan blades through the core air flowpathwhen the actuation device is installed in the gas turbine engine. Theconnection assembly includes a rotating to static transfer device.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and appinded claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the invention and, together with the description, serveto explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures, in which:

FIG. 1 is a schematic, cross-sectional view of a gas turbine engineaccording to an exemplary embodiment of the present disclosure.

FIG. 2 is a schematic, cross-sectional view of a forward end of a gasturbine engine in accordance with an exemplary embodiment of the presentdisclosure.

FIG. 3 is a perspective view of a portion of an exemplary actuationdevice in accordance with an exemplary aspect of the present disclosure.

FIG. 4 is a first view of a disk segment in accordance with an exemplaryembodiment of the present disclosure and a portion of the exemplaryactuation device of FIG. 3.

FIG. 5 is a second view of the exemplary disk segment of FIG. 4 and aportion of the exemplary actuation device of FIG. 3.

FIG. 6 is a cross-sectional view of a portion of a gas turbine engine inaccordance with an exemplary embodiment of the present disclosure, takenin a plane perpendicular to an axial direction.

Repeat use of reference characters in the present specification anddrawings is intended to represent the same or analogous features orelements of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to present embodiments of theinvention, one or more examples of which are illustrated in theaccompanying drawings. The detailed description uses numerical andletter designations to refer to features in the drawings. Like orsimilar designations in the drawings and description have been used torefer to like or similar parts of the invention. The terms “upstream”and “downstream” refer to the relative direction with respect to fluidflow in a fluid pathway. For example, “upstream” refers to the directionfrom which the fluid flows, and “downstream” refers to the direction towhich the fluid flows.

Referring now to the drawings, FIG. 1 is a schematic cross-sectionalview of a gas turbine engine in accordance with an exemplary embodimentof the present disclosure. More particularly, for the embodiment of FIG.1, the gas turbine engine is a high-bypass turbofan jet engine 10,referred to herein as “turbofan engine 10.” As shown in FIG. 1, theturbofan engine 10 defines an axial direction A (extending parallel to alongitudinal centerline 12 provided for reference), a radial directionR, and a circumferential direction C (see FIG. 3). In general, theturbofan 10 includes a fan section 14 and a core turbine engine 16disposed downstream from the fan section 14.

The exemplary core 16 of the turbofan engine 10 depicted generallyincludes a substantially tubular outer casing 18 that defines an annularinlet 20. The outer casing 18 encases, in serial flow relationship, acompressor section including a booster or low pressure (LP) compressor22 and a high pressure (HP) compressor 24; a combustion section 26; aturbine section including a high pressure (HP) turbine 28 and a lowpressure (LP) turbine 30; and a jet exhaust nozzle section 32. A highpressure (HP) shaft or spool 34 drivingly connects the HP turbine 28 tothe HP compressor 24. A low pressure (LP) shaft or spool 36 drivinglyconnects the LP turbine 30 to the LP compressor 22.

Additionally, for the embodiment depicted, the fan section 14 includes avariable pitch fan 38 having a plurality of fan blades 40 coupled to adisk 42 in a spaced apart manner. As depicted, the fan blades 40 extendoutwardly from disk 42 generally along the radial direction R.Additionally, each fan blade 40 is rotatable relative to the disk 42about a pitch axis P by virtue of the fan blades 40 being operativelycoupled to a suitable actuation assembly 48—the actuation assembly 48configured to vary a pitch of the fan blades 40 in a manner described indetail below. The fan blades 40 and disk 42 are together rotatable aboutthe longitudinal axis 12 by the LP shaft 36 across a power gear box 50.The power gear box 50 includes a plurality of gears for stepping downthe rotational speed of the LP shaft 36 to a more efficient rotationalfan speed. Additionally, for the embodiment depicted, the disk 42 of thevariable pitch fan 38 is covered by rotatable front hub 52aerodynamically contoured to promote an airflow through the plurality offan blades 40.

Referring still to the exemplary turbofan engine 10 of FIG. 1, theexemplary fan section 14 additionally includes an annular fan casing orouter nacelle 54 that circumferentially surrounds the fan 38 and/or atleast a portion of the core turbine engine 16. It should be appreciatedthat the nacelle 54 may be configured to be supported relative to thecore turbine engine 16 by a plurality of circumferentially-spaced outletguide vanes 56. Moreover, a downstream section 58 of the nacelle 54 mayextend over an outer portion of the core turbine engine 16 so as todefine a bypass airflow passage 60 therebetween.

During operation of the turbofan engine 10, a volume of air 62 entersthe turbofan 10 through an associated inlet 64 of the nacelle 54 and/orfan section 14. As the volume of air 62 passes across the fan blades 40,a first portion of the air as indicated by arrows 66 is directed orrouted into the bypass airflow passage 60 and a second portion of theair as indicated by arrow 68 is directed or routed into the LPcompressor 22. The ratio between the first portion of air 66 and thesecond portion of air 68 is commonly known as a bypass ratio. Thepressure of the second portion of air 68 is then increased as it isrouted through the high pressure (HP) compressor 24 and into thecombustion section 26, where it is mixed with fuel and burned to providecombustion gases 70.

The combustion gases 70 are routed through the HP turbine 28 where aportion of thermal and/or kinetic energy from the combustion gases 70 isextracted via sequential stages of HP turbine stator vanes 72 that arecoupled to the outer casing 18 and HP turbine rotor blades 74 that arecoupled to the HP shaft or spool 34, thus causing the HP shaft or spool34 to rotate, thereby supporting operation of the HP compressor 24. Thecombustion gases 70 are then routed through the LP turbine 30 where asecond portion of thermal and kinetic energy is extracted from thecombustion gases 70 via sequential stages of LP turbine stator vanes 76that are coupled to the outer casing 18 and LP turbine rotor blades 78that are coupled to the LP shaft or spool 36, thus causing the LP shaftor spool 36 to rotate, thereby supporting operation of the LP compressor22 and/or rotation of the fan 38.

The combustion gases 70 are subsequently routed through a jet exhaustnozzle section 82 of the core turbine engine 16 to provide propulsivethrust. Simultaneously, the pressure of the first portion of air 66 issubstantially increased as the first portion of air 66 is routed throughthe bypass airflow passage 60 before it is exhausted from a fan nozzleexhaust section 82 of the turbofan 10 also providing propulsive thrust.

It should be appreciated, however, that the exemplary turbofan engine 10described above with reference FIG. 1 is provided by way of exampleonly. In other exemplary embodiments, the exemplary turbofan engine 10may have any other suitable configuration. For example, in otherexemplary embodiments, the turbofan engine 10 may have any othersuitable number of, e.g., spools or shafts, compressors, and/orturbines.

Referring now to FIG. 2, a schematic, cross-sectional view of a forwardend of a turbofan engine 10 in accordance with an exemplary embodimentof the present disclosure is provided. In certain exemplary embodiments,the exemplary turbofan engine 10 of FIG. 2 may be configured insubstantially the same manner as exemplary turbofan engine 10 of FIG. 1.Accordingly, the same or similar numbering may refer to the same orsimilar part.

As depicted in FIG. 2, the turbofan engine 10 generally defines an axialdirection A and a radial direction R. Moreover, the turbofan engine 10defines a circumferential direction C (see FIG. 3) extending about theaxial direction A.

The fan 38 section 14 generally includes a variable pitch fan 38 havinga plurality of fan blades 40 coupled to a disk 42. More specifically,each fan blade 40 defines a base 86 at an inner end along the radialdirection R. Each fan blade 40 is coupled at the base 86 to the disk 42via a respective trunnion mechanism 88. The disk 42 includes a pluralityof bearings 90 such that the trunnion mechanism 88 is rotatably mountedwithin the disk 42—the trunnion mechanism 88 thus facilitating rotationof a respective fan blade 40 about a pitch axis P of the respective fanblades 40. Furthermore, as will be discussed in greater detail below,the exemplary turbofan engine 10 depicted includes an actuation device92 operable with the plurality of fan blades 40 for rotating theplurality of fan blades 40 about their respective pitch axes P.

For the embodiment depicted, the base 86 is configured as a dovetailreceived within a correspondingly shaped dovetail slot of the trunnionmechanism 88. However, in other exemplary embodiments, the base 86 maybe any suitable fan blade attachment feature for attaching the blade 40to the trunnion mechanism 88. For example, the base 40 may be attachedto the trunnion mechanism 88 using a pinned connection, or any othersuitable connection. In still other exemplary embodiments, the base 86may be formed integrally with the trunnion mechanism 88.

Further, as with the exemplary turbofan engine 10 of FIG. 1, the fan 38of the exemplary turbofan engine 10 depicted in FIG. 2 is mechanicallycoupled to the core 16. More particularly, the exemplary variable pitchfan 38 of the turbofan engine 10 of FIG. 2 is rotatable about alongitudinal axis 12 by an LP shaft 36 across a power gearbox 46 (seealso the embodiment of FIG. 1). For the embodiment depicted, the disk 42is attached to the power gearbox 46 through a fan rotor 94. The powergearbox 46 is, in turn, attached to the LP shaft 36, such that rotationof the LP shaft 36 correspondingly rotates the fan rotor 94, disk 42,and the plurality of fan blades 40. Notably, as is also depicted, thefan section 14 additionally includes a front hub 52 (which is rotatablewith, e.g., the disk 42 and plurality of fan blades 40).

Moreover, the fan 38 includes a static or stationary fan frame 96. Thefan frame 96 is connected through the core air flowpath 37 to the core16, or more particularly to an outer casing 18 of the core 16. For theembodiment depicted, the core 16 includes a forward strut, or vane, 98and a main strut 100, each providing structural support between theouter casing 18 of the core 16 and the fan frame 96. Additionally, theLP compressor 22 includes an inlet guide vane 102. The forward vane 98,main strut 100, and inlet guide vane 102 may additionally be configuredto condition and direct the portion of the flow of air over the fan 38provided to the core air flowpath 37 to, e.g., increase an efficiency ofthe compressor section.

Furthermore, the fan 38 includes one or more fan bearings 104 forsupporting rotation of the various rotating components of the fan 38,such as the plurality of fan blades 40. More particularly, the fan frame96 supports the various rotating components of the fan 38 through theone or more fan bearings 104. For the embodiment depicted, the one ormore fan bearings 104 include a ball bearing and a roller bearing.However, in other exemplary embodiments, any other suitable numberand/or type of bearings may be provided for supporting rotation of theplurality of fan blades 40. For example, in other exemplary embodiments,the one or more fan bearings 104 may include a pair (two) tapered rollerbearings, or any other suitable bearings. Additionally, in certainexemplary embodiments, the one or more fan bearings 104 may be formed ofany suitable material. For example, in at least certain exemplaryembodiments, the one or more fan bearings 104 may be formed of asuitable metal material, such as a stainless steel. Alternatively,however, in other exemplary embodiments the one or more fan bearings 104may include one or more components formed of a suitable ceramicmaterial.

Referring still to FIG. 2, as briefly discussed above, the turbofanengine 10 includes the actuation device 92 operable with the pluralityof fan blades 40 for rotating the plurality of fan blades 40 about theirrespective pitch axes P. In certain exemplary embodiments, the actuationdevice 92 may be configured in a similar manner as the exemplaryactuation assembly 48 of the embodiment of FIG. 1. As is depicted, theactuation device 92 includes an actuator 106 located outward of the coreair flowpath 37 of the turbofan engine 10. More specifically, for theembodiment depicted, the actuator 106 is positioned outward of the coreair flowpath 37 along the radial direction R, and further is positionedoutward of an LP compressor 22 of the compressor section of the core 16along the radial direction R. Additionally, for the embodiment depictedthe actuator 106 of the actuation device 92 is enclosed within a corecowl, i.e., outer casing 18, of the core 16 of the turbofan engine 10.However, in other exemplary embodiments, the actuator 106 may bepositioned in any other suitable location outward of the core airflowpath 37.

Moreover, the exemplary actuation device 92 depicted further includes aconnection assembly 108 extending from the actuator 106 for operablyconnecting the actuator 106 to the plurality fan blades 40 through thecore air flowpath 37. The exemplary connection assembly 108 generallyincludes a non-rotating mechanical coupling 110, a rotating to statictransfer device 112, and a rotating mechanical coupling 114. Theexemplary non-rotating mechanical coupling 110 extends between therotating to static transfer device 112 and the actuator 106, through thecore air flowpath 37, or more particularly, through the main strut 100of the core 16. Further, for the embodiment depicted, the non-rotatingmechanical coupling 110 is formed of one or more connection rods. Asused herein, the term “rods” refers to any substantially inflexiblemechanical component. Accordingly, the connection rods may be anysuitable rod, shaft, beam, etc. Further, the one or more connection rodsmay be formed of any suitable material, such as a suitable metalmaterial capable of withstanding an anticipated load thereon.

Moreover, for the embodiment depicted, the one or more connection rodsinclude a plurality of connection rods. The plurality of connection rodsdepicted are formed integrally at various joints 116, e.g., by welding.However, in other exemplary embodiments, the plurality of connectionrods may be rotatably or pivotably joined at the joints 116 to allow forsome angular movement between the attached connection rods duringoperation of the actuator 106. Additionally, in still other exemplaryembodiments, the one or more connection rods may be a single connectionrod bent or otherwise machined to the desired shape.

Furthermore, for the embodiment depicted, the rotating to statictransfer device 112 is positioned in the fan section 14 of the turbofanengine 10, inward of the core air flowpath 37. The rotating to statictransfer device 112 is formed generally of an inner race 118, an outerrace 120, and a plurality of bearings 122 located between the inner race118 and the outer race 120. The plurality of bearings 122 facilitate arelative movement between the inner race 118 and the outer race 120.Specifically, for the embodiment depicted, inner race 118 is a rotatableinner race configured to rotate with, e.g., the disk 42 and plurality offan blades 40, and the outer race 120 is a static outer race configuredto remain stationary relative to, e.g., the disk 42 and plurality of fanblades 40. Accordingly, for the embodiment depicted, the non-rotatingmechanical coupling 110 is attached to the static outer race 120, andthe rotating mechanical coupling 114 is attached to the rotating innerrace 118. However, in other exemplary embodiments, the outer race 120may instead be a rotatable outer race and the inner race 118 may be astatic inner race. In such an exemplary embodiment, the non-rotatingmechanical coupling 110 may be attached to the static inner race and therotatable mechanical couplings may be attached to the rotatable outerrace.

Referring now also FIGS. 3 through 5, the actuation device 92, andparticularly the rotating mechanical coupling 114, will be described ingreater detail. FIG. 3 provides a perspective view of the inner race 118of the rotating to static transfer device 112 along with the pluralityof rotating mechanical couplings 114 extending to the disk 42 of theexemplary turbofan engine 10; FIG. 4 provides a first view of anexemplary disk segment 124 (of the disk 42) and trunnion mechanism 88with a fan blade 40 at a first pitch angle; and FIG. 5 provides a secondview of the exemplary disk segment 124 (of the disk 42) and trunnionmechanism 88 with the fan blade 40 at a second pitch angle.

As is depicted, the actuation device 92 is attached to the plurality oftrunnion mechanisms 88 for rotating the plurality of fan blades 40 abouttheir respective pitch axes P. More specifically, the exemplaryactuation device 92 depicted includes a plurality of rotating mechanicalcouplings 114, which for the embodiment depicted are each alsoconfigured as a substantially inflexible rod, extending between therotating to static transfer device 112 and at least one of the pluralityof trunnion mechanisms 88. In certain exemplary embodiments, theplurality of rotating mechanical couplings 114 may each extend betweenthe rotating to static transfer device 112 and a respective one of theplurality of trunnion mechanisms 88. More particularly, as is shown mostclearly in FIG. 3, for the embodiment depicted, the exemplary actuationdevice 92 includes an individual rotating mechanical coupling 114extending from the rotating inner race 118 of the rotating to statictransfer device 112 to each of the plurality of trunnion mechanisms 88,such that each of the plurality of trunnion mechanisms 88 is attached tothe rotating to static transfer device 112 by a dedicated rotatingmechanical coupling 114.

Additionally, during operation of the actuation device 92, the actuator106 moves the entire connection assembly 108 linearly along the axialdirection A. Accordingly, for the embodiment depicted, the actuator 106of the actuation device 92 is configured as a linear actuator. Morespecifically, the actuator 106 may move the non-rotating mechanicalcoupling 110 in a forward direction or in an aft direction along theaxial direction A. For example, the actuator 106 may be configured as ahydraulic or electrical actuator attached to the non-rotating mechanicalcoupling 110 for moving the non-rotating mechanical coupling 110 alongthe axial direction A. The rotating to static transfer device 112transfers such linear movement of the non-rotating mechanical coupling110 to the rotating mechanical couplings 114. Notably, the rotatingmechanical couplings 114 and rotating inner race 118 of the rotating tostatic transfer device 112 are all rotatable with the plurality of fanblades 40, disk 42, and fan rotor 94.

Referring still to FIGS. 3 through 5, the linear movement of therotating mechanical couplings 114 along the axial direction A rotatesthe trunnion mechanisms 88, each of which in turn rotates a respectivefan blade 40 attached thereto. Such operation is depicted in FIGS. 4 and5. As shown, movement of the connection assembly 108 from a forwardposition (FIG. 4) aftwardly to an aft position (FIG. 5) rotates thetrunnion mechanisms 88 through the disk 42, or more particularly,through each of the respective disk segments 124, correspondinglyrotating the respective fan blades 40 about their pitch axes P.

Referring now briefly to FIG. 6, providing a schematic, cross-sectionalview of the turbofan engine 10 of FIG. 2 in a plane perpendicular to theaxial direction A, it should be appreciated that in certain exemplaryembodiments, the actuation device 92 may include a plurality ofactuators 106 spaced along the circumferential direction C—the pluralityof actuation devices 92 positioned above or radially outward of the coreair flowpath 37, and/or in the core cowl compartment (not labeled). Forexample, in the embodiment of FIG. 6, the turbofan engine 10 may includethree actuators 106 spaced evenly along the circumferential direction C(e.g., approximately 120 degrees apart).

However, in other exemplary embodiments, the actuation device 92 mayinclude any other suitable number of actuators 106 spaced in any othersuitable manner. For example, in other exemplary embodiments, theactuation device 92 may include a single actuator 106, two actuators106, four actuators 106, six actuators 106, or any other suitable numberof actuators 106. Further, in certain exemplary embodiments, theplurality of actuators 106 may move as a single unit to change a pitchof each of the plurality of fan blades 40 in unison. Alternatively,however, in other exemplary embodiments, the individual actuators 106may instead move relative to one another (e.g., at different ratesand/or amounts) to change a pitch of the plurality of fan blades in anon-uniform manner, such as in a cycloidal fashion. Such a configurationmay allow for utilizing the fan blades 40 in 1P mitigation.

It should also be appreciated that in still other exemplary embodiments,the actuation device 92 and/or turbofan engine 10 may be configured inany other suitable manner. For example, in other exemplary embodiments,any other suitable rotating to static transfer mechanism may be providedfor the exemplary actuation device 92. For example, although theexemplary rotating to static transfer mechanism includes two rows ofball bearings, in other exemplary embodiments, a single row of bearingsmay be provided, or any other suitable number of rows and/or types ofbearings may be provided. Additionally, although the exemplary actuator106 is depicted as a linear actuator movable generally along the axialdirection A, in other exemplary embodiments, the actuator 106 mayinstead be configured to move linearly at an angle relative to the axialdirection A, or alternatively may be configured as a rotary actuator, orany other suitable type of actuator. Moreover, although not depicted, inother exemplary embodiments, the actuation device 92 may include one ormore mounting features, pivotably or slidably mounting certaincomponents of the connection assembly 108 within the fan 38 section ofthe turbofan engine 10, within the strut (e.g., strut 100), and/orwithin the outer casing 18 of the core 16. Further, it should beappreciated, that the exemplary turbofan engine 10 depicted is providedby way of example only. For example, in other exemplary embodiments, theexemplary turbofan engine 10 may, e.g., include any suitable structuralconfiguration within the exemplary fan 38 section depicted.

A gas turbine engine including an actuation device according to one ormore of the exemplary aspects depicted may allow for the actuator ofsuch actuation device to be more easily accessible, such that theactuator of such actuation device may be more easily maintained and/orrepaired if needed (as compared to being located inward of the core airflowpath). Further, positioning of the actuator of the actuation deviceoutward of a core air flowpath of the gas turbine engine may simplify afan section of the gas turbine engine, as less or no hydraulic lines maybe required to extend therein, and thus an amount of pressurizedhydraulic fluid being transferred from a static frame of reference to arotating frame of reference may be reduced and/or eliminated.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims. It will be appreciated, thatwhen the definite article “said” is used in the claims prior to anelement, such use is to differentiate claimed elements fromenvironmental elements identified by the definite article “the” and notincluded within the claimed subject matter. Additionally, for claims notincluding the definite article “said”, the definite article “the” isused to identify claimed elements.

What is claimed is:
 1. A gas turbine engine comprising: a corecomprising in serial flow order a compressor, a combustor, and aturbine, the compressor, combustor, and turbine together defining a coreair flowpath; wherein the core further comprises a strut extendingthrough the core air flowpath; a fan section mechanically coupled to thecore, the fan section comprising a plurality of fan blades, each of theplurality of fan blades defining a respective pitch axis, each of theplurality of fan blades being rotatable about the respective pitch axis;and an actuation device operable with the plurality of fan blades forrotating the plurality of fan blades about the respective pitch axes,the actuation device comprising a rotating to static transfer device, anactuator located outward of the core air flowpath, and a non-rotatingmechanical coupling extending through the strut and between the rotatingto static transfer device and the actuator.
 2. The gas turbine engine ofclaim 1, wherein the actuator is a linear actuator.
 3. The gas turbineengine of claim 1, wherein the gas turbine engine defines a radialdirection, wherein the compressor comprises a low pressure compressor,and wherein the actuator of the actuation device is located outward ofthe low pressure compressor along the radial direction.
 4. The gasturbine engine of claim 1, wherein the rotating to static transferdevice comprises an inner race, an outer race, and a plurality ofbearings located between the inner race and the outer race.
 5. The gasturbine engine of claim 1, wherein the non-rotating mechanical couplingcomprises a plurality of connection rods.
 6. The gas turbine engine ofclaim 1, wherein the plurality of fan blades are rotatably attached to adisk using a plurality of trunnion mechanisms, and wherein the actuationdevice is connected the plurality of trunnion mechanisms for rotatingthe plurality of fan blades about the respective pitch axes.
 7. The gasturbine engine of claim 6, wherein the actuation device furthercomprises a rotating mechanical coupling extending between the rotatingto static transfer device and at least one of the plurality of trunnionmechanisms.
 8. The gas turbine engine of claim 7, wherein the actuationdevice further comprises a plurality of rotating mechanical couplings,wherein each of the plurality of rotating mechanical couplings extendsbetween the rotating to static transfer device and a respective one ofthe plurality of trunnion mechanisms.
 9. The gas turbine engine of claim1, wherein the gas turbine engine defines a circumferential direction,and wherein the actuation device further comprises a plurality ofactuators spaced around the gas turbine engine along the circumferentialdirection.
 10. The gas turbine engine of claim 1, wherein the core ofthe gas turbine engine is enclosed within a core cowl, and wherein theactuator of the actuation device is positioned within the core cowl.